Device for the production of a multi-layer fiber stock web

ABSTRACT

A machine for the production of a multi-layer fiber stock web, specifically a paper or cardboard web, whereby a first and a second layer are couched as a result of being delivered by an associated forming belt or wire to a couching element around which a second forming belt, or wire delivering the second layer is guided. This second forming belt, or wire impacts/runs onto the couching element before the second layer, which is supported by it, makes contact with the first layer. The second layer, at least in the location where it comes into contact with the first layer, is retained through suction force to the second forming belt wire.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The invention relates to a machine for the production of amulti-layer fiber stock web, specifically a paper or cardboard web.

[0003] 2. Description of the Related Art

[0004] Couching of various layers during paper production has hithertobeen accomplished by a couching roll, which is typically designed as aperforated cylinder. The forming belt, together with the second layer,or fiber stock web on it, are guided around this roll so that the rollis submerged into the continuous ribbon which is formed by a formingbelt or wire supporting the first fiber stock web. Pressure resultingfrom the tension of the forming belt or wire supporting the first fiberstock web or layer is exerted upon both layers or fiber stock webs.

[0005] Prior to couching of a fiber stock web, the second fiber stockweb is held to the couch roll only by the binding forces between thesecond fiber stock web and the second forming belt or wire.

[0006] In machinery and methods of the type known in the art there isthe risk at high speeds, that the second fiber stock web will separatefrom the second forming belt or wire prior to couching, due tocentrifugal force. This may result in a tangential throwing off of thefiber stock web, resulting in a related waste factor.

[0007] What is needed in the art is a device for the production of amulti-layer fiber stock web which would ensure that the second layerdoes not separate from the forming belt, or wire in the critical areaprior to couching.

SUMMARY OF THE INVENTION

[0008] The present invention provides a device and method in which thesecond fiber stock layer, in the area prior to the point at which itcomes into contact with the first fiber stock layer, is drawn withsuction force to the second forming belt, or wire. The second fiberstock layer is admitted specifically in the direction of the couchingelement. This second fiber stock layer is admitted in an area toward thesecond forming belt or wire, where this forming belt or wire is incontact with the couching element, or in the area it is diverted by thecouch element, or in the area in which it wraps around the couchelement.

[0009] This simple and reliable method ensures that the second layerdoes not separate from the second forming belt or wire in the criticalarea prior to couching. The appropriate handling additionally ensuresthat the web's dry content is increased.

[0010] In another embodiment of the invention, the couch element isformed by a support element having a surface area which is at leastpartially open faced and this support element is operated with aninterior pressure which is lower than the ambient pressure. The couchelement may, for example be a suction roll, a perforated cylinder or ashoe.

[0011] Advantageously, the second layer can be subjected to a suctionforce, which is produced by at least one suction zone in the couchelement.

[0012] Following the couch element, the forming belt or wire deliveringthe first layer accepts the second layer. The second forming belt orwire is appropriately separated from the first forming belt or wire inthe discharge area of the couch element.

[0013] In order to ensure delivery of the web, even at high speeds, itis advantageous if the second layer, in the area in which the twoforming belts or wires exit from the couch element, can be pushed awayfrom the couch element by means of fluid over pressure. This secondlayer separation from a forming belt may specifically be accomplishedwith air and/or steam. If steam is utilized as the pressure fluid, thena viscosity change of the two couched layers occurs enhancing thesubsequent dewatering of the web. For example, a steam blow box orsimilar device may be provided.

[0014] In yet another embodiment of the invention, the fluid excesspressure is produced by at least one pressure zone in the couch element.

[0015] The method according to the invention is characterized by thesecond layer being directed specifically through suction force towardthe second forming belt or wire, prior to the point at which it comesinto contact with the first layer.

[0016] The invention may also be utilized specifically at machineryspeeds of higher than 1000 m/min. The fiber stock webs that are to becouched may be created by optional methods, using optional formers (i.e.hybrid formers, gap formers, long wires, crescent formers, etc.), forexample, the following Voith Sulzer formers may be utilized: DuoFormerBase, DuoFormer Top, DuoFormer DK, DuoFormer D, TopFormer F, etc. Anycombination of various sheet forming methods are also possible.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above-mentioned and other features and advantages of thisinvention, and the manner of attaining them, will become more apparentand the invention will be better understood by reference to thefollowing description of an embodiment of the invention taken inconjunction with the accompanying drawings, wherein:

[0018]FIG. 1 is a schematic sectional illustration of a machine for theproduction of a multi-layer fiber stock web, in which two layers thatare to be couched are supplied to a couch zone, which is comprised of acouch element in the form of a perforated cylinder,

[0019]FIG. 2 is an enlarged illustration the couch zone equipped with aperforated cylinder, depicted in FIG. 1, and

[0020]FIG. 3 is an illustration of the couch zone, comparable to FIG. 2,whereby however, the couch element is a guide shoe.

[0021] Corresponding reference characters indicate corresponding partsthroughout the several views. The exemplifications set out hereinillustrate one preferred embodiment of the invention, in one form, andsuch exemplifications are not to be construed as limiting the scope ofthe invention in any manner.

DETAILED DESCRIPTION OF THE INVENTION

[0022] Referring now to the drawings, and more particularly to FIG. 1,there is shown a machine for the production of a multi-layer fiber stockweb 10.

[0023] Two layers or fiber stock webs 18 and 20, which are created inrespective formers 14 and 16, are supplied to couch zone 22 in whichthey are couched together.

[0024] Couch zone 22 comprises perforated cylinder 24 which serves as acouching element and to which layers 18 and 20 are supplied byrespective forming belts or wires 26 and 28. For the purposes of thisapplication a forming belt and a forming wire are functionallyequivalent, and when either term is used in this application it shallalso mean and refer to the other. As can be seen in FIG. 1, secondforming belt or wire 28 supplying second layer 20 is guided aroundperforated cylinder 24. Perforated cylinder 24, together with secondforming belt or wire 28, that is wrapped around perforated cylinder 24,is submerged into tensioned first forming belt or wire 26. Secondforming belt or wire 28 runs onto perforated cylinder 24, prior to thepoint where second layer 20, comes into contact with the first layer 18.

[0025] Referring additionally to FIG. 2, perforated cylinder 24 which isequipped with an at least partially open faced support area 30,including suction zone 32, through which second layer 20, at least inthe area of point S, at which second layer 20 comes into contact withfirst layer 18, is supplied with suction through second forming belt orwire 28, and is accordingly admitted to second forming belt or wire 28.Second layer 20 therefore, is supplied in the direction of perforatedcylinder 24, and is held onto second forming belt or wire 28 in an areain which it is diverted by and wraps around perforated cylinder 24.

[0026] Suction zone 32 is supplied with an interior pressure which islower than the ambient pressure.

[0027] Following perforated cylinder 24, second layer 20 is accepted byfirst forming belt or wire 26, which is supplying first layer 18. Secondforming belt or wire 28 is separated from first forming belt or wire 18in discharge area A of perforated cylinder 24.

[0028] Perforated cylinder 24 is additionally equipped with pressurezone 34 in order to push second layer 20 away from perforated cylinder24 by means of fluid over-pressure in the area in which forming belts orwires 26 and 28 are discharged from perforated cylinder 24. Possiblesources of fluid over-pressure include air and steam.

[0029] Another embodiment of the invention includes a GapFormer assecond former 16. Other formers are however, feasible. This also appliesto first GapFormer 14, which is indicated only by an arrow in thisexample. Combinations of various formers 14 and 16 are feasible.

[0030] As can be seen in FIG. 1, additional forming belt or wire 36 thatis allocated to former 16, is separated from second forming belt or wire28, before the wire runs onto perforated cylinder 24.

[0031] The present invention may include a support area 30 having acircular-cylindrical progression.

[0032] Now additionally referring to FIG. 3 there is another embodimentof the present invention wherein couch zone 22, which is comparable withFIG. 2, whereby the couch element however is guide shoe 24′.

[0033] Guide shoe 24′ is also equipped with suction zone 32 and pressurezone 34. Support surface area 30, which is at least partially openfaced, is curved differently in the area of zones 32 and 34. For examplethe radius of curvature, at least at the beginning of suction 32, islarger than in the area of pressure zone 34.

[0034] While this invention has been described as having a preferreddesign, the present invention can be further modified within the spiritand scope of this disclosure. This application is therefore intended tocover any variations, uses, or adaptations of the invention using itsgeneral principles. Further, this application is intended to cover suchdepartures from the present disclosure as come within known or customarypractice in the art to which this invention pertains and which fallwithin the limits of the appended claims.

What is claimed is:
 1. A machine for the production of a multi-layerfiber stock web, comprising: a first former including a first formingwire, said first former configured to form and convey a first fiberlayer; a second former including a second forming wire, said secondformer configured to form and convey said second fiber layer; a couchelement, said second forming wire being guided around said couchelement, said first forming wire configured to convey said first fiberlayer to a place of contact with said second fiber layer, said place ofcontact defining a couch zone, said couch element and said secondforming wire being configured to be in contact prior to said couch zone;and a suction device configured to provide suction through said secondforming wire to said second fiber layer in said couch zone.
 2. Themachine of claim 1, wherein said machine is configured to supply saidsecond fiber layer from said second former to said couch element.
 3. Themachine of claim 1, wherein said machine is configured to supply saidsecond fiber layer to an area where said second wire is in contact withsaid couch element.
 4. The machine of claim 1, wherein said machine isconfigured such that said second fiber layer is supplied in one of anarea in which said second fiber layer is deflected by said couch elementand an area in which said second fiber layer wraps around said couchelement.
 5. The machine of claim 1, wherein said couch element is asupport element, said support element having a partially open face and ahollow interior, said support element being configured to accept aninterior pressure of less than ambient pressure.
 6. The machine of claim5, wherein said support element includes said suction device, saidsupport element configured to provide suction to said second fiberlayer.
 7. The machine of claim 1, wherein said couch element is one of asuction roll and a perforated cylinder.
 8. The machine of claim 1,wherein said couch element is a shoe.
 9. The machine of claim 1, whereinsaid machine is configured such that said first wire conveys said secondfiber layer following said couch element.
 10. The machine of claim 1,wherein said machine is configured such that said second wire separatesfrom said first wire in an area of said couch element.
 11. The machineof claim 1, wherein said couch element includes at least one pressuredischarge element which acts on an area defining at least one pressuredischarge zone.
 12. The machine of claim 11, configured such that saidsecond fiber layer is acted upon by a fluid medium in at least one saidpressure discharge zone.
 13. The machine of claim 11, wherein at leastone of said at least one pressure discharge element delivers fluid underpressure in at least one said pressure discharge zone.
 14. A method forthe production of a multi-layer fiber web, comprising the steps of:forming a first fiber layer on a first wire; forming a second fiberlayer on a second wire; delivering said second fiber layer by way ofsaid second wire to a couch element, such that said second wire is incontact with said couch element prior to said second fiber layercontacting said first fiber layer; couching said second fiber layer tosaid first fiber layer using said couch element; and applying a suctionforce to said second fiber layer through said second wire in an areawhere said second fiber layer contacts said first fiber layer.
 15. Themethod of claim 14, wherein said second fiber layer is supplied fromsaid second former to said couch element.
 16. The method of claim 14,wherein said second fiber layer is supplied in the area where saidsecond wire is in contact with said couch element.
 17. The method ofclaim 14, wherein said second fiber layer is supplied in one of an areain which said second fiber layer is deflected by said couch element andan area in which said second fiber layer wraps around said couchelement.
 18. The method of claim 14, wherein said couch element is asupport element, said support element having a partially open face and ahollow interior with a pressure less than ambient.
 19. The method ofclaim 18, wherein said applying step is accomplished utilizing saidsupport element.
 20. The method of claim 14, wherein said couch elementis one of a suction roll and a perforated cylinder.
 21. The method ofclaim 14, wherein said couch element is a shoe.
 22. The method of claim14, wherein said first wire conveys said second fiber layer followingsaid couch element.
 23. The method of claim 14, wherein said second wireseparates from said first wire in an area of said couch element.
 24. Themethod of claim 14, further comprising the step of discharging pressurein said couch element using at least one pressure discharge element,said pressure discharge element acting on an area defined as at leastone pressure discharge zone.
 25. The method of claim 24, wherein saiddischarging step uses a fluid medium in at least one said pressuredischarge zone to act upon said second fiber layer.
 26. The method ofclaim 24, wherein said discharging step uses pressurized fluid in atleast one said pressure discharge zone.